2 Schuster, Rate at which Ions are Generated. 



In a closed space it is not very difficult with delicate 

 electrometers to determine the rate at which ions are 

 formed, but observation shews that it depends on the 

 nature of the material composing the enclosure, and it 

 would be wrong to argue that the formation of ions in 

 the free atmosphere is the same as that measured in a 

 closed vessel. 



The present paper deals with the description of a 

 method of measuring the rate at which recombination 

 takes place in a particular sample of air. When the ionic 

 density (the number of ions per cubic centimetre) is 

 known, the measurement allows us to calculate the rate 

 at which ions are being produced. 



The left hand portion of the accompanying figure 



A 



A ~^ V" 



represents Ebert's apparatus in a diagrammatic form. E is 

 a tube about 3 centimetres wide, and 40 centimetres 

 long. -^ is a box containing a turbine driven by clock- 

 work, which sucks air through the tube at the rate of 

 I •6 litres per second, giving a linear velocity for the 

 air in the tube of 233 cms./second. An insulated rod 

 runs along the axis of the tube E, and in connexion with 

 the rod, the figure shews the aluminium leaves of one of 

 the very beautiful electroscopes of Elster and Geitel's 

 construction. If the rod is charged negatively, the air 

 passing through the space forming a cylindrical condenser 

 gradually discharges it, and provided the electric force is 

 sufficiently strong, all the positive ions are given up to 

 the rod. Knowing the volume of air passing in a given 

 time, and the capacity of the condenser, the quantity of 

 electricity given up to the electroscope is measured by 



